A new asymmetrical winding common mode choke capable of attenuating differential mode noise

A new asymmetrical winding Common Mode (CM) choke capable of attenuating the Differential Mode (DM) noise is proposed in this paper. In case of conventional symmetrical winding CM choke, the CM and DM noises are attenuated by the magnetizing and leakage inductors of CM choke, respectively. However, since the number of turns is limited by the shape and size of the CM choke, it is very difficult to obtain the enough leakage inductor to eliminate the DM noise thoroughly. For this reason, the bulky choke should be used for the larger leakage inductor or another choke is usually used for the only DM noise attenuation. Therefore, the cost and size of EMI filter using conventional CM choke might be increased. In order to solve these problems, the asymmetrical winding CM choke is introduced in this paper. Different from the conventional symmetrical CM choke, the magnetizing inductor of the proposed CM choke can suppress not only CM but also DM noise. Therefore, the proposed choke can effectively attenuate the CM and DM noises even with the smaller size and lesser number of turns. It can be applied to the whole kind of power converters which use two or three wire system. To confirm the validity and superiority of the proposed choke, the comparative results of measured total, DM and CM noise characteristics between conventional and proposed chokes are presented. Finally, a practical approach to designing EMI filters and design procedure are proposed and discussed.